of: fdt: Remove weak early_init_dt_mark_hotplug_memory_arch()

Commit 41a9ada3 ("of/fdt: mark hotpluggable memory") introduced
two (for systems with and without memblock) weak versions of
early_init_dt_mark_hotplug_memory_arch(), that could be overridden by an
architecture-specific version.  However, no overrides ever emerged.
Later, commit aca52c39 ("mm: remove CONFIG_HAVE_MEMBLOCK")
removed the non-memblock version.

Remove early_init_dt_mark_hotplug_memory_arch(), and replace it by a
direct call to memblock_mark_hotplug().

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/1a61f75ec50d3c2922fcdbe33337266a58a4125f.1628671960.git.geert+renesas@glider.be


Signed-off-by: Rob Herring <robh@kernel.org>